The present invention relates to a brake system for motor vehicles with an actuating unit that is made up of a pneumatic brake force booster as well as a master brake cylinder located downstream of the booster, with such master brake cylinder having wheel brakes connected to it, wherein the control valve of the brake force booster can be actuated independently of the driver's actions by means of an electromagnet, whose armature can actuate one of the control valve's sealing seats, and with a brake pressure controller, to which a signal corresponding to a nominal brake pressure and a signal corresponding to the actual brake pressure are supplied and whose output variable corresponds to a nominal value of the electric current to be supplied to the electromagnet.
This type of brake system is known from the international patent application WO 95/03196. In the known system the output variable of the brake pressure controller, which corresponds to a nominal path of the electromagnetic armature, is compared with a signal that corresponds to the actual path of the electromagnetic armature, whereby a control difference corresponding to the result of the comparison is supplied to a position controller that affects the position of the control valve and whose output variable represents the electric current to be supplied to the electromagnet.
A less advantageous feature of the known system is the necessity of using a position controller that has to be able to realize very short cycle times and, hence, has a complicated structure and is very expensive. The displacement sensor, which is needed to sense the actuating path of the electromagnetically actuatable sealing seat, is another cost factor.
Consequently, it is the object of the present invention to propose measures, by means of which the above-mentioned system components could be eliminated and, consequently, considerable price reductions could be achieved.